WestJet said its load factor, or the percentage of seats filled with paying customers, jumped to 86.1 percent. That compares with 82.7 percent a year earlier and marks the Calgary-based airline's eighth consecutive record monthly load factor.

WestJet shares jumped C$1.19, or 5.2 percent, to C$24.26 on the Toronto Stock Exchange in early trade on Tuesday.

WestJet, which will launch a regional carrier called Encore in June, said that capacity, which is measured by available seat miles, rose just 3.1 percent. Traffic, or revenue per passenger mile, increased by 7.3 percent.

Toll Cross Securities analyst Jacques Kavafian said traffic gains matched his estimates, while capacity growth was less than he expected.

"This translates into a huge increase in load factor and therefore, margins," he said in a note. Based on traffic data released to date, he expects WestJet will report first-quarter earnings of 61 Canadian cents per share, over 49 Canadian cents a share last year.

National Bank Financial analyst Cameron Doerksen said WestJet's traffic is a "clear indication of healthy air travel demand" and suggests that the airline is benefiting from a charter deal with Thomas Cook Group (TCG.L).

WestJet struck an agreement with Thomas Cook last April to be the exclusive airline for the UK travel group's tour operator business in Canada. WestJet is the only airline providing seat capacity for Thomas Cook's tour operator arm, Sunquest, in the Canadian market.

Air Canada ACb.TO, the country's biggest airline, is expected to report is monthly statistics later on Tuesday.

Despite the declines, Porter chief executive Robert Deluce said that yield, or revenue per available seat mile, "is holding up nicely compared to last year despite significant capacity increases by other carriers on certain routes."

Porter competes with Air Canada and WestJet on certain short-haul flights in Canada and a handful of routes to the United States.